Foursquare

Foursquare is the epitome of location-based social networking. It survived the early firestorms and buyouts of the post-mobile GPS world to become one of the most popular, richest apps on iPhone and other platforms. The basic premise of Foursquare is that you use it while you're out and about and "check in" to the places you visit. It

Created by Dennis Crowley and Naveen Selvadurai in 2007, it's grown to include photographs, tips, lists, and much, much more.